In a tire vulcanizer which performs a vulcanization process of a tire in a high-pressure and high-temperature state, generally, a bag-shaped bladder which presses the tire accommodated in a mold from the inside is provided. There may be cases where the bladder is mounted on a center mechanism provided at the center portion of a support structure which supports a lower mold. A fluid as a vulcanizing medium such as steam, hot water, or gas such as nitrogen can be supplied into and discharged from the bladder via a supply and discharge passage formed in the center mechanism. When the tire is pressed, the bladder is allowed to inflate by the vulcanizing medium (for example, see PTLs 1 to 3).
As illustrated in FIG. 11, the center mechanism 130 includes a guide member 131, a bag head 137, and a center post 146. The guide member 131 is mounted in a through-hole 125 which is formed at the center of a support structure 113. The bag head 137 is elevated along the guide member 131. The center post 146 is elevated in a guide hole 136 which is formed at the center portion of the bag head 137. An upper clamp ring (not illustrated) which grips the upper portion of the bladder (not illustrated) is mounted on the upper end portion of the center post 146. A lower clamp ring (not illustrated) which grips the lower portion of the bladder is mounted on the bag head 137.
The center post 146 forms the piston rod of a center post cylinder 144 which is disposed below the bag head 137. Otherwise, the center post 146 is connected to the tip end portion of the piston rod of the center post cylinder 144 by a screw or the like and slides along with the piston rod. A bead lift cylinder 141 is mounted on the center post cylinder 144 via a bracket 140.
For example, as the center post cylinder 144 is extended, the upper end portion of the center post 146 protrudes upward from the bag head 137, and the outside diameter of the bladder decreases. Accordingly, the bladder can be inserted into the inside from the bead of the tire, or the bladder can be separated from the inner peripheral surface of the tire.
In a case where the bead lift cylinder 141 is extended, the bag head 137 is displaced upward together with the center post 146, and the bead portion of the vulcanized tire which is accommodated in a mold (not illustrated) is pressed upward to be released from the mold.
The support structure 113 that supports the mold from below includes, for example, a lower platen 114, a support plate 116, and a heat insulating material 115. The lower platen 114 is a hot plate which heats the mold. The support plate 116 supports the lower platen 114 from below. The heat insulating material 115 is provided between the lower platen 114 and the support plate 116, and blocks heat of the lower platen 114.
In the support plate 116 of the support structure 113 illustrated in FIG. 11, a piston 117 which is operated by a fluid such as air, nitrogen gas, water, or oil is provided. The mold which is displaced in an opening direction due to an increase in the internal pressure or the like can be pressed by the piston 117 in a closing direction.
The upper end portion of the guide member 131 included in the center mechanism 130 described above includes a flanged portion 133 which extends outward in a radial direction. The flanged portion 133 is fixed to the peripheral edge portion of the through-hole of the lower platen 114 from above by a bolt or the like. Accordingly, the guide member 131 is fixed to the support structure 113. The guide member 131 includes a small diameter portion 135 of which the inside diameter is slightly larger than the outside diameter of an inner cylinder that extends downward from the bag head 137, and a large diameter portion 134 which has a larger inside diameter than that of the small diameter portion 135 and of which the upper edge is provided with the flanged portion 133. A restriction portion 170 is formed in the outer peripheral surface of the upper portion of the bag head 137.
The restriction portion 170 is disposed at a position where the end portion thereof on the outside in the radial direction is closer to the outside in the radial direction than the inner peripheral surface of the small diameter portion 135 of the guide member 131 and is closer to the inside in the radial direction than the inner peripheral surface of the large diameter portion 134. Accordingly, in a case where the bag head 137 slides toward the small diameter portion 135 of the guide member 131 and is located at a predetermined elevated position, the restriction portion 170 of the bag head 137 collides with a stepped portion between the small diameter portion 135 and the large diameter portion 134 of the guide member 131. As a result, the displacement of the bag head 137 toward the small diameter portion 135 is restricted.